An overrunning clutch is a well known device for selective transmission of torque between a driving member and a driven member. In a conventional embodiment the clutch comprises a cylindrical outer race and a cylindrical inner race. A plurality of sprags are retained in the radial space between the races. Each sprag essentially functions as a strut placed between the races to mechanically couple them by a wedging action when either race is rotated in the driving direction. However, rotation of either race in the opposite (or overrunning) direction frees the sprags and the races are decoupled. Either race may be the driven member or driving member.
In the overrunning mode of operation each of the plurality of sprags experiences some wear from moving contact with the race surfaces. In applications where high RPM is a normal operating parameter, e.g. electrical power stations, the rubbing contact of the sprags in the overrunning mode can be a limiting factor on clutch life.